Implantable medical devices are used to treat various disorders. For example, stents are used to treat coronary heart disease. According to the American Heart Association, coronary heart disease is the single leading cause of death in America today. Coronary heart disease is caused by atherosclerotic narrowing of the coronary arteries and can produce angina pectoris and/or heart attack in patients. Stents can be used to open an artery that has been cleared by balloon angioplasty or as an alternative to balloon angioplasty. Typically, stents are collapsed to a small diameter, placed over an angioplasty balloon catheter, and placed in the area of the blockage. As the balloon is inflated, the stent expands and forms a scaffold to hold the artery open. The stent stays in the artery permanently, holds it open, improves blood flow to the heart muscle and relieves symptoms (usually chest pain). Restenosis or reclosing of the vessel, however, can occur in stented vessels. To help prevent restenosis, patients undergo systemic antiplatelet and anticoagulant therapy.